THREE DAYS after Donald E. Gates was released from prison after serving 28 years for a murder he didn't commit, federal prosecutors acknowledged that they received, but failed to act on, information discrediting testimony key to his conviction. In the same week, a Florida man imprisoned for 35 years for kidnapping and rape was freed after DNA tests proved his innocence. As appalling as the two cases are, what's even scarier is the thought that imperfections in the criminal justice system will go uncorrected and more people could be wrongly jailed.

The wrongful conviction of Mr. Gates in the 1981 rape and murder of a D.C. woman and that of James Bain in the 1974 assault of a 9-year-old boy could serve as primers for what's wrong with the system. In Mr. Bain's case, it was reliance on identification from an unreliable eyewitness: a traumatized 9-year-old. Witness misidentification is the single greatest cause of wrongful convictions, contributing to more than 75 percent of convictions overturned through DNA testing nationwide, the Innocence Project reported.

The second biggest cause is faulty forensics, and that played a starring role in Mr. Gates's conviction. A FBI special agent testified that two pubic hairs found on the victim's body were microscopically identical to those of Mr. Gates. Even if, as later examination showed, the agent hadn't basically been making up his findings, the science behind the technology is suspect. Indeed, a report this year from the National Research Council found such serious deficiencies in the nation's forensic science system that it called for major reforms and new research.

It's also clear from Mr. Gates's case that improvements are needed in how the government discloses information. Even after a 1997 inspector general's report questioned the credibility of FBI agent Michael P. Malone, prosecutors were still, as late as this year, touting his findings. Only after the D.C. public defender's office did its own digging were the problems with Mr. Malone's performance, and the government's failure to disclose them, brought to light.

In a letter to the court admitting that they had received information almost six years ago that called Mr. Gates's conviction into doubt, prosecutors at the U.S. Attorney's Office said that they have referred the matter to the Justice Department's Office of Professional Responsibility. They also should follow the lead of states such as North Carolina in establishing innocence commissions that bring together judges, police, prosecutors, defense attorneys and victim's advocates in an attempt to identify the practices that lead to wrongful convictions and to recommend reforms.